A gas sensor of this type is discussed, for example, in German Published Patent Application No. 197 07 456. The gas sensor includes a metal housing in which two molded ceramic parts are positioned axially one behind the other, which include openings for receiving a sensor element. Between the molded ceramic parts is an intermediate space, in which a glass seal that surrounds the sensor element is provided. The molded ceramic part is sealed in the housing by a sealing ring.
The gas sensor discussed in German Published Patent Application No. 197 07 456 provides that when a seal is introduced into a molded ceramic part, the danger of cracking is high due to temperature fluctuations during operation of the gas sensor. In addition, the sealing between the molded ceramic part and the housing requires complex manufacturing technology.
German Published Patent Application No. 197 51 424 discusses a gas sensor including a metal housing in which a molded ceramic part including a recess for receiving a sensor element is arranged. The molded ceramic part encircles the sensor element in its center. The end of the sensor element facing the measuring gas includes one or more measuring elements, e.g., electrochemical cells. At the end of the sensor element facing away from the measuring gas, contact surfaces, which are connected electrically by contacting with conductor elements leading out of the gas sensor, are arranged on the sensor element. Between the molded ceramic part and the end of the sensor element facing the contacting, the sensor element is enclosed by a glass seal. The glass seal is positioned in a metal receptacle which is affixed to the housing by a welded connection. The metal receptacle, the end of the sensor element facing the contacting, and the contacting are surrounded by a metal sleeve, which in turn is connected to the housing by an additional welded connection.
To produce the sensor elements for such gas sensors, ceramic sheets imprinted with functional layers are laminated together and sintered. During sintering, the ceramic sheets shrink. In this process, slight warping of the sensor elements is often unavoidable. The recess of the molded ceramic part for receiving the sensor element is therefore dimensioned so that the sensor element has play in the recess. Since the sensor element is fixed only at its end facing the contacting by a positive material connection, the sensor element is able to vibrate in the recess due to the vibrations that occur in operation, which may result in damage to the sensor element. Furthermore, building the sensor element into the rigid molded ceramic part is complex, requires difficult production techniques, and may damage the sensor element.